Taffykay writes: Because it's very difficult to send large spaceships constructed on earth into space, Tethers Unlimited (TUI) has proposed to employ robotic 3-d printers that look like giant spiders to build the spacecraft — from space. The ‘SpiderFab’ would in theory enable in-orbit fabrication of large spacecraft components such as antennas, solar panels, trusses, and other multifunctional structures.